Terminal outlet for industrial furnaces



May 7, 1940. s. P. LESSMANN TERMINAL OUTLET FOR INDUSTRIAL Flmmcfi FiledApril 25. 1959 WITNESSES:

ATTORNEY Patented May 7, 1940 TERMINAL OUTLET FOR INDUSTRIAL FURNACESGerhard P. Lessmann, Wilkinsburg, 2a., assignmto Westinghouse Electric &Manufacturing Company, East Pittsburgh, Pin, a corporation ofPennsylvania Application April 25,- 1939, Serial No. zeaozz 8 Claims.

In electric furnaces, particularly of the type encased in a metallicshell, means must be provided to convey electric power from outside ofthe furnace to the electric heating means within the 5 furnace. For thispurpose, an outlet conductor or terminal of some sort, connected at oneend to the electric heating means and at the other end connectible topower lines, passes through the wall of the furnace and a hole in theshell. A 10 terminal outlet structure is generally employed to securethe conductor in position with respect to the hole in the shell, and ina manner to prevent the conductor from contacting the metal shell. Myinvention relates to such a terminal 15 outlet strucure, and,preferably, for a furnace in which a charge is to be heat-treated whileenveloped in an inert or protective gaseous atmosphere so that theterminal outlet structure must not only position the conductor withrespect to 20 the hole in the shell, but must also be gas-tight toprevent leakage or seepage of the atmosphere through the terminal outletstructure.

It is an object of my invention to provide a terminal outlet structurewhich is simple of design and assembly, economical of manufacture, andone which will be reliable and permanent in use.

It is a further object of my invention to provide a terminal outletstructure which will be 0 gas-tight, and which will not be subject tobreakage because of pressure applied thereto in order to secure agas-tight construction.

It is still another object of my invention to provide a terminal outletstructure which will position the outlet conductor in the hole of theshell through which it passes by a simple and novel means, so that thepossibility of short-circuits or other faults to the metallic shell issubstantially eliminated.

In accordance with my invention, I secure to the shell a. plurality (inthe particular instance,

four) of elongated, outwardly-extending bolts, in spaced relation aboutthe hole. A plurality of pieces of asbestos board are crossed in thespaces 45 between the bolts and are provided with openings which canencompass the conductor. Because the boards are crossed, they co-operatewith the conductor so that the conductor cannot be moved, although,without the conductor, each board 50 might have one degree of freedom ofmovement,

that is, movement in one direction. A steel pressure plate has holesfitting the bolts, and the aforesaid insulating boards are clamped withpacking provisions to insure a gas-tight structure 55 between the plateand shell by nuts on the bolts.

My construction, as briefly described above, has certain definiteadvantages. One of these advantages lies in the simplicity by which theasbestos boards can be made. They do not need apertures fitting aroundthe bolts, but it is sum- 5 cient to make them of a width to snugly fitbetween bolts. This construction eliminates drilling bolt-holes in theboards, and also the necessity of aligning the bolts and such holesduring the assembly of the terminal outlet structure. 10

Another advantage of my invention lies in the manner in which the boardsare clamped. Clamping pressure is distributed over a substantial area ofthe faces of the boards so that no indiscriminately applied andconcentrated pressures will cause cracking of the boards due to boltforces.

The above and other objects, features and all-- vantages of my inventionwill be apparent from the following description of a specific embodimentthereof, taken in conjunction with the drawing, in which:

Figure 1 is a sectional view of a terminal structure for an outletconductor coming through a wall of a furnace;

Fig. 2 is a view taken on the line II--H of Fig.

Fig. 3 is a view taken on the line III-III of Fig. l, with the clampingplate and bolt nuts removed;

Fig. 4 is a view of the large side of one of the asbestos boards;

Fig. 5 is a longitudinal, vertical sectional view of the board of Fig.4;

Fig. 6 is a view of the flat side of the clamping plate; and,

Fig. 7 is an edge view of the plate of Fig. 6.

My invention, as has already been indicated, is particularly adapted toelectric furnaces which are provided with electric heating means. Theelectric heating means is preferably of the resistor ribbon type and thefurnace may have two, or considerably more, outlet conductors for theseresistor ribbons. The number of outlets, of course, is a matterdetermined in the design of the furnace, and it is suiiicient for thepurpose of 0 describing my invention to show but one outlet conductorand terminal outlet structure therefor.

Accordingly, in Fig. 1, a furnace wall 2 is shown but fragmentarily andthe outside of this wall is encased by a. metallic sheath or shell 4, asis customary with furnaces of this type. However, it should bedistinctly understood that the shell 4 may, in some instances, be but aplate embedded or secured to the wall purposely to provide a means tosecure a terminal outlet structure in accordance with my invention.

The wall 2 is provided with a hole 6, and the shell 4 is provided withan enlarged hole 8 so that the outlet conductor l8 may passtherethrough. The outlet conductor may be a rod of suitable alloy andits inside end may be welded to a bar l2 which, in turn, may be weldedto an end I4 of a resistor ribbon. If desired, a second end l6 ofanother resistor ribbon may also be welded or otherwise secured to theoutlet conductor ID.

The furnace wall 2 is itself electrically insulating, but the metallicshell 4 is, of course, a conductor of electricity. Accordingly, it isnecessary to provide a terminal structure which will maintain theconductor l away from the edges of the hole 8 in the shell 4. Moreover,since my invention is particularly adapted for furnaces employing ,aprotective atmosphere within their heating chamber, the terminal outletstructure must, in addition, seal the openings 8 and 8 so that none ofthe protective atmosphere can leak or seep out, or atmospheric air leakor seep into the furnace.

The terminal outlet structure comprises, in this specific embodiment,four bolts 18, 28, 22 and 24, arranged at the corners of a quadrilateraland, preferably, a square or rectangle. The shell 4 is provided withsuitable apertures through which the bolts may pass, and the heads ofthe bolts are welded to secure them in place to the shell in a gas-tightmanner so that there can be no leakage of gas through the bolt-holes inthe shell. Crossed between the bolts are two boards, 28 and 28 made ofan electricity-insulating material, such as, for example, asbestos. Theboards are similar in construction but assembled differently in theterminal outlet structure to obtain an outlet structure to maintain theconductor fixed in position.

The structure of each of the boards is shown more particularly in Figs.4 and 5, and comprises a central opening 38, conically countersunk, orotherwise formed in any suitable manner to provide an enlarged, taperedcavity 32,

The boards are rectangular in shape and are of a width substantiallyequal to the distance between pairs of aligned bolts, that is, one ofthe boards 28 is of a width substantially equal to the minimum distancebetween the pair of bolts l8 and 20, and the pair of bolts 22 and 24;while the board 28 is of a width substantially equal to the minimumdistance between the pair of bolts l8 and 24 and the pair of bolts 28and 22, as shown in greater detail in Fig. 3. The length of these boardsis somewhat greater than the corresponding dimensions of thequadrilateral between the four bolts. Accordingly, it may be observedthat each board has one degree of freedom of movement only. Thus, forexample, the board 28 can slide in the direction of its length only, andthe board 26 can slide in a direction at right angles to the possiblesliding direction of the board 28.

If now the boards are made to surround the conductor II], it is obviousthat the conductor is fixed in position, since one of the boardsprevents sliding movement of the conductor in the one direction and theother in the perpendicular direction. The conductor, therefore, will becentered or properly positioned, with respect to the hole 8 in the shell4, if the asbestos boards are r mped in their respective positions,shown in Fig. 3. To this end, a rigid clamping plate 34, which may be ofsteel, is provided having an enlarged central hole or opening 38 andholes 38, 48, 42 and 44 through which the bolts 18, 28, 22 and 24 may,respectively. pass. Suitable nuts 48, 88, 52 and 84 clamp the asbestosboards between the plate 34 and the shell 4. The boards 28 and 28, andthe plate 34 are, of course, first slipped over the conductor l0 beforethe nuts are applied to the bolts and tightened.

Since the conductor passes through the asbestos boards and the openings38 in each of the boards, and has only slight clearance with respectthereto, it is obvious that the boards are maintained and positionedwith the cooperation of the conductor l8 and since each of the boardsprevents movement in any direction perpendicular to the conductor I8,with respect to Fig. 1, the terminal outlet structure therefor rigidlypositions the conductor I8, not only with respect to the hole 8 of theshell 4, but also with respect to the central hole 38 of the plate 34,it being understood that the last two holes are sumciently large withrespect to the conductor l8 so that insulating clearance is provided.

The cavities 32 of the boards aid in rendering the terminal structuregas-tight. In assembling the boards on the conductor III, the cavity ofthe inner board 26 faces the cavity of the outer board 28, with acompressible packing material, such as, for example, asbestos rope 58interposed. A gasket 58 is also provided around the hole 8. when thenuts are tightened on their respective bolts, the packing 56 iscompressed tightly against the tapered sides in the boards defining thecavities, and also against the surfaces of the conductor III which itcontacts.

It is obvious that enough packing 58 must be used to assure a gas-tightjoint. The required amount can be judged by the distance between theboards 26 and 28. In the assembled structure, it is preferred to have avery slight clearance between these boards when the nuts are completelytightened so that the packing must necessarily be pressed against theconductor in. The structure, therefore, completely seals the terminaloutlet since the gasket 58 prevents leakage of protective atmospherebetween the shell and the lower board, and the packing 56 preventsleakage of atmosphere along the axis of the conductor I 8.

It may be observed that the outer end 60 of the conductor i0 is threadedto permit the bolting on of power cable lugs after the assembly of theterminal output structure.

One of the marked advantages of my construction lies in the distributionof the clamping pressure of the bolts through the asbestos boards which,obviously, will be transmitted through a substantial area of the plate34 and the cavities 32 to the gasket 58.

In accordance with the objects of my invention, therefore, I haveprovided a terminal struc ture in which only the plate 34 has holeswhich align with the bolts i8, 20, 22 and 24, while the boards 26 and 28are merely positioned between the bolts. It is obvious that a number ofbolts other than four may be employed as, for example, three boltsarranged in a triangle with three asbestos boards to insure cancellationof the freedom of. movement of each board. It is, therefore, obviousthat equivalents of my invention will be apparent to those skilled inthe art and I desire that the appended claims be so considered.

I claim as my invention:

1. A terminal outlet structure primarily for an electric furnace,comprising the combination with a metallic shell for said furnaceprovided with a hole, and a conductor passing through said hole, saidconductor being of smaller diameter than said hole; of a plurality ofinsulating boards having means through which said conductor passes,means for confining said boards each to diflerent directions of freedomof movement parallel to said shell, means to clamp said boards to saidshell, said means cooperating with said boards and conductor for fixingsaid conductor away from the edges of said shell that define the saidhole therein.

2. The sti'ucture of claim 1 in which the last said means includes anouterplate and bolts extending from said shell and passing through asuitable holes in said plate.

3. A terminal outlet structure primarily for an electric furnace,comprising the combination with a metallic shell for said iumaceprovided with a hole, and a conductor passing through said hole spacedfrom its edges; of a plurality, in excess of two, of bolts extendingoutward from said shell and spaced about said hole, a plurality ofcrossed, insulating boards between said bolts and fitted to spacesbetween the said bolts, said boards having aligned openingssubstantially fitting the said conductor through which said conductorpasses, at least one of said openings in said boards being countersunkon the side toward another of said boards, compressible packing in thecountersunk portion, a plate having opemngs through which said boltspass, and also an enlarged opening through which said conduc-- torpasses, and fastening means on said bolts for compressing said boardsbetween said shell and said plate.

4. The structure of claim 3 including a gasket between the shell and theboard adjacent to it.

5. A terminal outlet structure primarily for an electric furnace,comprising the combination with a metallic shell for said furnaceprovided with a hole, and a conductor passing through said hole spacedfrom its edges; of a plurality, in excess of two, 01' bolts extendingoutwardly from said shell and spaced about said hole, at least twoinsulating boards fitted to, and in spaces, between said bolts andsubstantially contacting the said bolts on the sides toward said spaces,said boards having openings through which the conductor passes, saidboards being crossed so as to maintain the position of said conductoragainst displacement.

6. A terminal outlet structure primarily for an electric i'urnace,comprising the combination with a metallic shell for said furnaceprovided with a hole, and a conductor passing through said hole spacedfrom its edges; of four bolts extending outward from said shell, andspaced about said hole, forming a pair of crossing spaces betweenopposed pairs of said bolts, an insulating block in one of said spacessubstantially contacting said bolts on the sides toward one space, asecond insulating block having a side toward the first said board anddisposed in the other of said spaces, substantially contacting saidbolts on the sides toward said other space, said boards having aperturesin the overlapping parts of said spaces and through which said conductorpasses, a rigid plate abutting the other side of the second saidinsulating board, said plate having an aperture through which saidconductor passes spaced from its edges, and additional apertures throughwhich the said bolts pass, and means to clamp said boards between saidshell and said plate.

7. The structure of claim 6 in which the contiguous parts of saidopenings on said boards are enlarged and tapered, and a compressiblepacking is inserted in said parts in contact with said conductor, and agasket is provided between said shell and said boards.

8. A terminal outlet structure primarily for an electric furnace,comprising the combination with a metallic shell for said Iumaceprovided with a hole, and a conductor passing through said hole spacedfrom its edges; of a plurality, in excess of two, oi. bolts extendingoutward from said shell and spaced about said hole, a plurality ofcrossed, insulating boards between said bolts and fitted to spacesbetween the said bolts, said boards having aligned openingssubstantially fitting the said conductor, at least one of said openingsin said boards being countersunk on the side toward another of saidboards, compressible packing in the countersunk portion, and means toclamp said boards to said shell whereby said packing is compressedagainst said conductor.

GERHARD P. LESSMANN.

